A citadel is typically a large fortress or a large structure built around a castle to protect it from attacks, disasters, or calamities.
The Harappan Civilisation built the oldest known citadels. Harappan Civilization settlements were classified into two types:
Citadel was designated for areas that were smaller in size but higher in elevation, while Lower Town was designated for areas that were larger but lower in elevation.
Citadel’s main feature was that the buildings were built higher on mud-brick platforms, physically separated from the lower town. Baked brick walls were built around the sections, which were strong enough to last a thousand years.
For the general public, the Citadel in Mohenjo Daro served two purposes:
Warehouse: a massive structure made of wood from the upper section and brick from the lower section.
Great Bath: a large rectangular tank in the courtyard that was surrounded by walls and had rooms. It also had a well-thought-out drainage system.
Final Answer:
Many Harappan cities were divided into two or more sections. The section to the west was smaller but higher than the other sections. Citadel refers to this small and high area of the city.